The present invention relates to computer programming and, in particular, to a method and system for maintaining sessions with a host computing application and securely allocating the sessions to a client computing application.
The growth of the Internet presents software developers with new market demands and new options for publishing data stored on enterprise computing systems, such as mainframe computers and mid-range computers like IBM""s AS/400 series. Enterprise computing systems refer to the entire computing system for a whole corporation, especially computing systems spanning across the various locations in which a corporation maintains offices. Thus, enterprise computing refers to the computing system of the whole corporate enterprise. Enterprise computing typically includes those computing applications upon which a corporation derives a great deal of its revenues, such as order entry, accounts receivable, payroll, and inventory. An enterprise network refers to systems such as wide area networks (xe2x80x9cWANsxe2x80x9d), local area networks (xe2x80x9cLANsxe2x80x9d), and Internet working bridges. An enterprise solution typically pertains to software that enables individuals and groups within a large corporation to use computers in a network environment to access information from a wide range of sources, collaborate on projects, and communicate easily with text, graphics, video, or sound.
Many corporations, and other large organizations, would like to develop applications that display, format, and manipulate data from their host legacy enterprise applications in ways that are not possible with the conventional character mode, screen-based applications available on their host enterprise computing systems. A legacy system, such as that provided by screen-based host enterprise computing systems, refers to a computer program, network, or other computing element that remains in use after a business or organization has installed new computing systems, such as a graphical user interface (xe2x80x9cGUIxe2x80x9d) program. Each department within the corporation may wish to develop its own custom view of the enterprise data available on the host enterprise computing system. For example, the sales department may wish to view the enterprise data required for sales forecasting in a graphical format. The marketing department may wish to publish a sales catalog on an Internet web server and provide dynamically updated inventory information. The accounts receivable department may wish to sort payment records according to the amount owed or the length of time the balance has been outstanding. Such customization is cumbersome at best, and perhaps impossible, using conventional screen-based host applications.
Many corporations would also like to migrate their data storage mechanisms to new computing environments without affecting the enterprise applications that rely upon the stored enterprise data. Screen-based host applications typically run on large to medium-size computing systems, such as IBM mainframes, IBM AS/400s, Unisys computers, and Digital VAX computing systems. Applications for such computing systems have typically been designed for use with character mode terminals and are based on individual screens. Character mode terminals, also known as text mode terminals or alphanumeric mode terminals, display letters, numbers, and other text characters but not graphical images or WYSIWYG (xe2x80x9cwhat-you-see-is-what-you-getxe2x80x9d) character formatting, such as italics and superscript. Some conventional emulation systems have been developed that emulate character mode terminals on more modern PC-based computing systems in order to interface with host applications. However, these emulation systems are both cumbersome and limited in their capabilities.
In conventional host enterprise computing systems, a screen-based application program accesses enterprise host computer data primarily through host terminal screens. The screen-based host interface, leftover from the early days of computing, has become outdated, unfamiliar, and cumbersome in the modern world of point-and-click GUI applications. In this new world of computing, many corporations want to transition from screen-based applications to user-friendly GUI applications without disrupting mission-critical business processes. This new computing environment challenges programmers to make sure that enterprise host data is manageable, secure, and consistently available to clients. In a LAN or on the Internet, a xe2x80x9cclientxe2x80x9d refers to a computer that accesses shared network resources provided by another computer, known as a xe2x80x9cserver.xe2x80x9d
Embodiments of the present invention provide a Session Allocation Manager (xe2x80x9cSAMxe2x80x9d) that manages multiple client connections to a limited number of host sessions available from a host computing application. The SAM also minimizes the latency involved in creating and terminating a host session for the client computing system that requested the session. Embodiments of the SAM may establish connections with screen-based host applications, customer information control system (xe2x80x9cCICSxe2x80x9d) applications, and database applications.
Embodiments of the SAM reside on a server in the communication path between a client application and a host application, and data objects may use the SAM to associate a client connection with a host session. The SAM monitors session activity between the client and the host, and enforces inactivity timeouts. The SAM also attempts to reestablish a connection to a host session when the connection fails.
In an environment having only a limited number of available sessions, the SAM controls a client""s session requests for a host application by creating one or more sessions with the host application and then allocating one of the sessions to the client upon request. For example, a connection mechanism associated with the client application may request a session from the SAM for connection to the host, according to an embodiment of the invention. After the connection mechanism has received the session, then the connection mechanism may transmit data between the client application and the host application via the SAM. If multiple client applications share a connection mechanism, the SAM may dedicate a particular session to that connection mechanism. The SAM performs a vital management function, and in its absence client-host communications may not perform as efficiently or as securely as possible.
Embodiments of the invention provide a method and system for managing multiple connections between client computing applications and host computing applications that have a limited number of available connections. With each request from a session client application to allocate a session, the SAM receives a session name. The SAM matches the session name with a session name in its pre-existing collection of session names. The SAM then accesses a session having the matching session name. The SAM connects the host to the session and allocates the session to the client. For each request from a client application to transfer data with host, the SAM receives configuration objects that include access methods for exchanging data between the host and the client. The SAM manages the resulting data transfer between the client and the host, according to an embodiment of the invention.
Embodiments of the invention provide a SAM having a first object interface that includes methods and properties for creating and controlling sessions between hosts and clients. An object interface contains a set of logically related function members. For example, if an object were a xe2x80x9cword processor,xe2x80x9d one interface may perform edits and have function members such as xe2x80x9cdelete.xe2x80x9d Each session contains directions for managing communications between a client and a host. The SAM also provides a second object interface that accesses a session and allocates the session to the client requesting the session. The SAM further provides a third object interface that establishes a session interface with the host and makes a session communications link available to the client.
Embodiments of the invention provide a computer-readable medium holding computer-executable instructions for performing a method for managing connections between clients and hosts. For each connection request from a client, the SAM receives a host name and a session name. The SAM then accesses a session matching the session name and allocates the session to the client.